1. Field of the Invention
The present invention relates to an apparatus for recording and/or reproducing data, such as digital audio/video (A/V) data, and a control method thereof. More particularly, the present invention relates to an apparatus for recording and/or reproducing data, such as digital A/V data, which detects a point of scene change for the purpose of searching the data received and stored therein, and generates navigation data using the detected point of scene change, and a control method thereof.
2. Description of the Related Art
Generally, a ‘navigation’ function of a data recording and/or reproducing apparatus, such as an A/V data recording and/or reproducing apparatus, refers to moving from a current data reproducing point to another point selected by a user and resuming reproducing from the user selected point, or rearranging the reproducing order of the recorded A/V data as desired by the user so that reproducing can be performed in the rearranged order. Accordingly, the ‘navigation data’ refers to additional information that is provided to realize the navigation function, and includes a data row temporal search table that contains information corresponding to the recording position of the A/V data and reproducing time for the corresponding A/V data, and a program table that contains reproducing order rearranging information preset by a manufacturer.
While reproducing the A/V data of the digital satellite broadcasting or the digital high resolution broadcasting from a 2-dimensional medium such as optical disc, it is the scene change information that is generally used for the function that enables the user to perform a search function to skip some scenes or jump to his desired scene and resume reproducing therefrom.
In particular, the scene change information is the information required for the reproducing process of the A/V data recording and/or reproducing apparatus that records/reproduces A/V data together with the navigation data. For example, one viewer can have all the TV programs of a certain broadcasting station of the previous day recorded on a single disc. Instead of watching all the recorded programs from the first one, the viewer may want to skip some parts of the program, and it is the scene change information that is required for such a situation.
The scene change information refers to the information about the pointer which points to a certain position of the entire region of the program. When the viewer inputs a command such as “search command” that requires skipping of some scenes in the forward or backward direction, the pointer moves from the position currently being reproduced to a new reproducing position requested by the viewer. The scene change information can be recorded according to several criteria.
One existing method for detecting a scene change from the recording medium for A/V content search is to perform a discrete cosine transformation (DCT) based on the complexity of the image in the pixel region, and detect the scene change based on the resultant information. The major shortcoming of this existing method is that it has quite great computational requirements for the sequential processes of decoding a compressed image in MPEG format, recovering the image, re-DCT computation, and detection of scene change in real time basis. Accordingly, it requires a system that has enough capability to handle the required computations.
As for the detection algorithm that segments the digital multimedia motion picture into plurality of meaningful parts, there mainly are two methods. One method is to use pixel data of reference image, and the other is to use motion compensation of an image frame. The simplest way is to use the difference between the pixel data of the two neighboring frames. That is, if the difference is determined to be equal to, or greater than a predetermined threshold, it is determined that there is scene change. Although this technique may be effective with respect to the picture that has relatively little motion, it has considerable errors for a picture that has much motion. The method to use motion compensation is more effective on these accounts. However, the shortcoming is that it has complex computational requirements for motion vectors of the respective frames. Although phase matching can be employed for this method, it requires many computations and memory to perform fast Fourier transform (FFT).
As described above, such complex computations required for the scene change detection hinder adaptation of the above method in a system of relatively low capacity, such as a satellite broadcasting receiver or the like.